This invention generally relates to medical devices for drainage of fluids, and more specifically to ureteral stents.
Ureteral stents are used to assist urinary drainage from the kidney to the bladder in patients with ureteral obstruction or injury, or to protect the integrity of the ureter in a variety of surgical manipulations. Stents may be used to treat or avoid ureter obstructions (such as ureteral stones or ureteral tumors) which disrupt the flow of urine from the kidneys to the bladder. Serious obstructions may cause urine to back up into the kidneys, threatening renal function. Ureteral stents may also be used after endoscopic inspection of the ureter.
Ureteral stents typically are tubular in shape, terminating in two opposing ends: a kidney distal end and a bladder proximal end. One or both of the ends may be coiled in a pigtail or J-shape to prevent the upward and/or downward migration of the stent due, for example, to physiological movements. A kidney end coil is designed to retain the stent within the renal pelvis and to prevent stent migration down the ureter. The bladder end coil sits in the bladder and is designed to prevent stent migration upward toward the kidney. The bladder coil is also used to aid in retrieval and removal of the stent.
Ureteral stents, particularly the portion positioned in the ureter near the bladder and inside the bladder, may produce adverse effects including blood in the urine, a continual urge to urinate, strangury, and flank pain accompanying reflux of urine up the stent (e.g., when voiding) as pressure within the bladder is transmitted to the kidney. In short, stents may cause or contribute to significant patient discomfort and serious medical problems.
The present invention concerns a ureteral stent that avoids patient discomfort and urine reflux upward toward the kidney. Patient discomfort induced by the use of a foreign body may be decreased with devices that are as small and flexible as possible in the lower (bladder) end of the ureter and in the bladder itself. Rather than rely on a tubular structure of a substantial set thickness for the entire length of the ureteral stent, the invention concerns a stent with a thin flexible wall at the proximal region of the stent. When the stent is placed within the urinary system of a patient, the proximal region of the stent generally is located in or near the end of the ureter at the junction of the ureter and the urinary bladder and also in the bladder itself, and the distal region generally is located in the kidney and in or near the other end of the ureter at the junction of the ureter and the kidney. In general, the thin-walled proximal region of the stent is sized and configured to extend along at least part of the ureter near the bladder, and may cross the ureteral vesicle junction, and into the bladder. The ureteral vesicle junction is a particularly sensitive region of the ureter and is the source of much of the discomfort resulting from the presence of an installed stent. It also is possible, and in some cases desirable, to use a stent with a thin wall throughout substantially all of its length, from near the kidney retention structure to the proximal region.
The stent wall of the middle and distal regions may be constructed of a material of greater thickness than the proximal region in order to resist the pressure from the adjacent tissue that would collapse the ureter if not for the presence of the stent. The middle region is the elongated region of the stent between the distal region and a transition zone found near the proximal region. Towards the proximal region of the stent, the inner diameter of the wall that exists in the middle and distal regions increases, resulting in a comparatively thinner wall in the proximal region of the stent, while the outer diameter of the stent is constant or substantially constant over the entire length of the stent. The thin wall region can be positioned at or near the ureteral vesicle junction. The thin wall construction at the proximal region of the stent produces a softer and more flexible segment of the stent which decreases the irritation to the surrounding tissues while allowing for normal urine drainage and resistance to urine reflux.
In one aspect, the invention relates to a medical device for assisting the drainage of fluid from a body cavity. The medical device includes an elongated segment extending from a distal region through a transition zone to a proximal region, the segment having a substantially constant outer diameter and an inner wall. The inner wall defines a lumen having an inner diameter in the proximal region that is greater than the inner diameter in the distal region. The transition zone may extend through a middle segment of the stent or all the way from a middle segment to the proximal end. The variation of the inner diameter in the transition zone may be linear or non-linear, steep or smooth, continuous or combinations thereof. The variation of the inner diameter may be quantic resulting in a step change. In one embodiment, the medical device is a stent. In another embodiment the medical device is a ureteral stent.
In some embodiments, the transition zone has no longitudinal length thus forming a step in the inner diameter between the proximal and distal regions. The step forms a surface for contacting a pusher during implantation of the medical device in the body cavity. In other embodiments, the segment includes a pliable proximal region.
In yet other embodiments the medical device further includes at least one member extending through at least some of the lumen to the proximal region. The member may include a flexible material. The member may include a thread. In other embodiments the member is secured to an inner wall. The member may also include a substantially noncompressible material. In some embodiments, the member includes a loop.
In yet another embodiment, the elongated segment includes a retention structure in the distal region. The retention structure may be kink resistant. The retention structure may include a coil.
The device may further include a second segment including an exterior wall contacting at least a portion of the inner wall of the elongated segment, and further including an inner wall defining a lumen coaxial with the lumen of the elongated segment. The second segment may include a surface disposed at a proximal region for contacting a pusher during implantation of the medical device in the body cavity. In one embodiment, the exterior wall of the second tubular segment provides an interference fit with the inner wall of the first segment. In another embodiment, the transition zone includes varying inner diameters of the inner wall between the distal region and the proximal region.
In another embodiment, the medical device includes at least one member extending from the second segment. In yet another embodiment, the member is secured to the elongated segment. In another embodiment, the member includes a flexible material. The member may also include a substantially noncompressible material. The member may include a thread. In some embodiments, the member includes a loop.
In still another aspect, the invention relates to a medical device for assisting the drainage of fluid from a body cavity, the device including an elongated segment having an annular wall defining a lumen, the lumen extending from a distal opening to a proximal opening. The annular wall having a thickness near the distal opening greater than near the proximal opening, wherein the elongated segment is kink resistant near the distal opening and pliable near the proximal opening.
In one embodiment, the medical device includes a stent. The medical device may also include a ureteral stent. In another embodiment, the medical device includes at least one member extending from and attached to the elongated segment. In yet another embodiment, the member includes a thread. In yet another embodiment, the medical device may further include a second segment including an exterior wall contacting at least a portion of the inner wall of the elongated segment, and further including an inner wall defining a lumen coaxial with the lumen of the elongated segment.
In another aspect, the invention relates to a method for treatment of blockage of urine flow from a kidney to a urinary bladder. The method includes providing a medical device and inserting the device in a ureter for assisting the drainage of fluid from a body cavity. The medical device includes an elongated segment extending from a distal region through a transition zone to a proximal region, the segment having a constant outer diameter and an inner wall defining a lumen having an inner diameter in the proximal region that is greater than the inner diameter in the distal region. In an embodiment, the method further includes positioning the distal region of the medical device near a renal pelvis and positioning the proximal region of the medical device in a urinary bladder. In an embodiment, the method includes positioning the transition zone of the stent at least partly upstream of the ureteral junction.
In another embodiment, the method further includes a second segment including an exterior wall contacting at least a portion of the inner wall of the elongated segment, and further comprising an inner wall defining a lumen coaxial with the lumen of the elongated segment.
In another aspect, the invention relates to a method for treatment of blockage of urine flow from a kidney to a urinary bladder. The method includes providing a medical device and inserting the device in a ureter for assisting the drainage of fluid from a body cavity. The medical device includes an elongated segment having an annular wall defining a lumen, the lumen extending from a distal opening to a proximal opening. The annular wall includes a thickness near the distal opening greater than near the proximal opening, wherein the elongated segment is kink resistant near the distal opening and pliable near the proximal opening. In an embodiment, the method further includes positioning the distal region of the medical device near a renal pelvis and positioning the proximal region of the medical device in a urinary bladder. In an embodiment, the method includes positioning the transition zone of the stent at least partly upstream of the ureteral junction.
The positioning of a stent may include the use of a pusher. In one embodiment, the distal end of the pusher contacts a surface of the stent in the transition zone. In another embodiment, the distal end of the pusher is tapered and directly abuts the stent in the transition zone. In yet another embodiment, the pusher contacts a surface on a second segment disposed within the lumen of the stent near the transition zone.
The foregoing and other aspects, embodiments, features, and advantages of the invention will become apparent from the following description, figures, and claims.